$max_price_query = new WP_query(array(
    'posts_per_page' => -1,
    'post_status' => 'publish',
    'post_type' => 'properties',
    'nopaging' => true,
    'orderby' => 'meta_value_num',
    'meta_key' => '_price',
    'order' => 'DESC',
));

if ($max_price_query->have_posts()) {
    while ($max_price_query->have_posts()) : $max_price_query->the_post();
        $pid = $post->ID;
        $price_max = get_post_meta($pid, '_price', true);
        echo '<pre>' . $pid . '</pre>';
    endwhile;
    wp_reset_postdata();
}

function set_query_parameters($query) {
    if( !is_admin() &&  is_main_query() && is_post_type_archive( 'properties' ) ) {
        $query->set('meta_key', '_featured_prop');
        return $query;
    }
      add_action( 'pre_get_posts', 'set_query_parameters' );